JP2013079603A - Condensing equipment for axial flow exhaust type steam turbine and geothermal power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide condensing equipment for an axial exhaust type steam turbine and a geothermal power plant which can secure a nozzle request pressure and reduce a construction cost.SOLUTION: The condensing equipment for the axial flow exhaust type steam turbine includes: a steam turbine 1 to which steam is supplied; a condenser 2 which condenses steam exhausted from the steam turbine as directly contacting cooling water from a spray nozzle 3; a cooling tower 4 which generates cooling water by accumulating condensed water and cooling water; a water circulating pipe which supplies water condensed by the condenser 2 to the cooling tower; and a water return circulating pipe 5 which returns the cooling water generated by the cooling tower 4 to the condenser unit and where a pump 8 is arranged at the water return circulating pipe 5.

Description

  The present invention relates to a condensing device for an axial exhaust steam turbine used in a geothermal power plant or the like, and a geothermal power plant equipped with such a condensing device.

  A geothermal power plant is provided with a condensing device that rotates a steam turbine using natural steam generated by geothermal heat, and then cools and condenses exhaust to recover condensate. The condensing device has a direct contact type in which the cooling water is directly contacted with the exhaust from the steam turbine, and the direct contact type condenser uses a tray and the cooling water is directly sprayed by spraying. Then, there is a method using a spray nozzle that contacts exhaust.

  In the spray nozzle system, a plurality of nozzles are installed at appropriate positions in the condenser in order to spray circulating water using the spray nozzles in the condenser.

  Each nozzle needs to have a pressure required for spraying, and the nozzle installed at the top must also have a pressure.

Here, the pressure required for the nozzle is expressed by the following equation (1).
Nozzle required pressure = pressure difference (cooling tower inner pressure (atmospheric pressure)-condenser internal pressure (lower than atmospheric pressure))
-Pressure loss (valves, piping)
-Hydrostatic head difference (top height of condenser spray nozzle installation-cooling tower water level) (1)

  Thus, the installation height of the condenser and cooling tower is the difference between the pressure difference between the internal pressure of the cooling tower and the internal pressure of the condenser, the pressure loss of the piping and the control valve, the height of the spray nozzle and the water level of the cooling tower. It is necessary to consider the hydrostatic head difference.

  In the above formula (1), the pressure difference between the cooling tower inner surface pressure and the condenser internal pressure and the pressure loss of the piping and the control valve are determined by the system design. In order to secure the required nozzle pressure, it is necessary to lower the installation position of the spray nozzle in order to consider the hydrostatic head difference between the maximum spray nozzle installation height of the condenser and the water surface level of the cooling tower. As a result, there was a problem that the excavation of the condenser deepened and the construction cost increased.

  In addition, the conventional geothermal power plant mainly employs a lower exhaust type that exhausts the steam turbine downward, so that the phenomenon that the cooling water from the return circulation water pipe flows into the steam turbine, that is, the wart induction does not occur. There was no need to consider. However, in the lower exhaust type, it is necessary to dig the condenser to a position lower than the steam turbine, which causes an increase in construction cost.

  Therefore, in recent years, in order to reduce the construction cost and further reduce the pressure loss from the final blade outlet of the steam turbine to the condenser, an axial exhaust type is applied to the steam turbine and installed at the same level as the steam turbine. An increasing number of such condensers adopting an axial exhaust type that directs exhaust directly from the rear side of the last blade of the steam turbine.

  When such an axial exhaust type is adopted, the level of water accumulated in the condenser, that is, the hot well level, is adjusted so that all the control valves installed in the return circulating water pipes when the circulating water pump is emergency stopped. It is necessary to consider that the turbine water-induction caused by the cooling water flowing into the condenser before closing will not occur.

  Specifically, the hot well level of the condenser must be set in consideration of the level rising from the lowest blade level of the last stage blade of the steam turbine due to the amount of cooling water flowing into the condenser.

  Here, the higher the water level of the cooling tower, the larger the hydrostatic head difference from the hot well level of the condenser, and the amount of cooling water flowing into the condenser increases until the control valve is fully closed. Along with this, there has been a problem that the height required for cooling water storage increases, the hot well level needs to be lowered, the condenser is deeply dug, and the construction cost increases.

  As a conventional direct contact condensing device for an axial exhaust type steam turbine, there is one described in Patent Document 1 below. This device forms a rising part in the return circulating water pipe, and a siphon breaker consisting of a branch pipe and a valve is connected near the top of the rising part, so that when the circulating water pump is stopped, the cooling tower is connected to the condenser. This is to prevent cooling water from flowing in and prevent warping.

JP 2001-193417 A

  However, what is described in the above-mentioned Patent Document 1 is to prevent the warpage in the direct contact condensing device for an axial exhaust type steam turbine, and in order to ensure the nozzle required pressure, The problem of deeper digging and increased construction costs could not be solved.

  In view of the above circumstances, in the condensing device for an axial exhaust type steam turbine, the present invention is for an axial exhaust type steam turbine capable of ensuring the nozzle required pressure, reducing the construction cost, and further preventing the wartion. It aims at providing a condensing apparatus and a geothermal power plant.

A condensing device for an axial exhaust steam turbine according to an aspect of the present invention includes:
A condenser that condenses the steam exhausted from the steam turbine by directly contacting cooling water from the spray nozzle;
A cooling tower that receives and accumulates water condensed by the condenser and generates the cooling water;
A circulating water pipe for supplying the water condensed by the condenser to the cooling tower;
A return circulation water pipe for supplying the cooling water generated by the cooling tower to the condenser;
With
A pump is arranged in the return circulation water pipe,
From the pressure difference obtained by subtracting the internal pressure of the condenser from the internal pressure of the cooling tower, a value obtained by subtracting the hydrostatic head difference obtained by subtracting the water surface level of the cooling tower from the maximum installation height of the spray nozzle of the condenser is It is characterized by operating to satisfy the required pressure of the spray nozzle.

  According to the condensing device for an axial exhaust type steam turbine and the geothermal power plant of the present invention, it is possible to secure the required nozzle pressure, reduce the construction cost, and prevent the war- taction.

BRIEF DESCRIPTION OF THE DRAWINGS It is the arrangement | positioning figure which showed the structure of the condensing apparatus for axial flow exhaust type steam turbines and geothermal power plant by Embodiment 1 of this invention. FIG. 3 is an explanatory diagram showing a relationship between a lifting height of a circulating water pump and a height of a turbine building in the condensing device for an axial exhaust type steam turbine and the geothermal power plant according to the first embodiment. It is the arrangement | positioning figure which showed the structure of the condensing apparatus for axial flow exhaust type steam turbines and geothermal power plant by Embodiment 2 of this invention. It is the arrangement | positioning figure which showed the structure of the condensing apparatus for axial flow exhaust type steam turbines and geothermal power plant by Embodiment 3 of this invention.

  Hereinafter, an axial exhaust type steam turbine condensing device and a geothermal power plant according to embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
A condensing device for an axial exhaust steam turbine according to Embodiment 1 of the present invention and a geothermal power plant including the same will be described with reference to FIG.

  Steam flows from a steam pipe (not shown) into the steam turbine 1, works in the steam turbine 1, is exhausted, and flows into the spray-type direct contact condenser 2.

  A spray nozzle 3 is arranged inside the condenser 2, and the cooling water supplied from the cooling tower 4 through the circulating water pipe 5 is sprayed and directly contacts the steam. Thereby, the steam exhausted from the steam turbine 1 is condensed and becomes condensate and accumulates in the lower part of the condenser 2 together with the cooling water.

  The accumulated water is boosted by the circulating water pump 6, and the flow rate is adjusted by the control valve 9. The accumulated water is sent to the cooling tower sprinkling pipe 7 installed at the upper part of the cooling tower 4, sprinkled and cooled by air cooling. Accumulate at the bottom of 4.

  The water accumulated in the cooling tower 4 returns as cooling water to the spray direct contact condenser 2 through the pump 8 in the return circulation water pipe 5 as will be described later.

Here, as shown in FIG. 1, the level of each element is expressed as follows.
L1: Water surface level of cooling tower 4 L2: Maximum height of installation of spray nozzle 3 inside condenser 2 L3: Installation level of condenser 2 (digging level)
L4: Installation level of cooling tower 4 L5: Maximum height of cooling tower 4 L6: Hot well level of condenser 2 L7: Final blade blade level of steam turbine 1 L8: Installation level of steam turbine 1 (of rotating shaft height)
L9: Sprinkling pipe installation level of cooling tower 4

The required pressure ΔP1 of the spray nozzle 3 is expressed by the following equation (2) based on the above equation (1).
ΔP1 = Pressure difference (cooling tower inner pressure (atmospheric pressure)-condenser internal pressure (lower than atmospheric pressure)
-Pressure loss (valves, piping)
-Hydrostatic head difference ΔP2 (Condenser spray nozzle installation top height L2-Cooling tower water level L1) (2)

  In this formula (2), in order to assist in securing the required pressure ΔP1 of the spray nozzle 3, the present embodiment 1 is characterized in that a pump 8 is installed in the return circulation water pipe 5. Thereby, it is not necessary to satisfy the required pressure ΔP1 by the hydrostatic head difference ΔP2, and the following effects can be obtained.

  i) In order to consider the hydrostatic head difference ΔP2, the necessity to lower the spray nozzle installation height L2 of the condenser 2 and to deepen the installation level (digging level) L3 of the condenser 2 is eliminated. Construction cost can be reduced.

  Alternatively, in order to consider the hydrostatic head difference ΔP2, the necessity of increasing the installation level L4 of the cooling tower 4 or the height L5 of the cooling tower 4 in order to increase the water surface level L1 of the cooling tower 4 is eliminated. The restriction due to the head difference ΔP2 is eliminated, and the construction cost is reduced.

  ii) The hydrostatic head difference ΔP2 can be lowered. For this reason, the flow rate of the cooling water flowing into the condenser 2 from the cooling tower 4 is reduced before the control valve 9 is fully closed. As a result, even if the level difference (L7−L6) between the hot well level L6 of the condenser 2 and the last stage blade level L7 of the steam turbine 1 is set to be small, it is possible to prevent the warming.

  As a result, the installation level (digging level) L3 of the condenser 2 can be increased, that is, the digging amount can be reduced, or the installation level L8 of the steam turbine 1 can be lowered, and the following effects can be obtained. can get.

  a) Since the hot well level L6 of the condenser 2 can be increased and the digging level L3 of the condenser 2 can be reduced, an effect of reducing the construction cost can be obtained.

  b) FIG. 2 shows a state where the steam turbine 1, the condenser 2, and the circulating water pump 6 are installed in the turbine building 20. When the circulating water pump 6 breaks down, it is necessary to lift and transport the inside of the turbine building 20 with a crane or the like. As described above, when the circulating water pump 6 is installed indoors together with the steam turbine 1, the height of the turbine building 20 is set to the height at which the circulating water pump 6 is lifted when the circulating water pump 6 breaks down, and the highest in the turbine building 20. It is necessary to determine the height considering the allowable height H of the carry-out route passing above the existing equipment.

  As shown in FIG. 2, the equipment having the highest height in the turbine building 20 is, for example, a turbine casing that integrally covers the steam turbine 1 and the condenser 2, or a generator (not shown) and the steam turbine 1. In the case where it is attached to the steam turbine 1 such as a phase separation bus, the installation level L8 of the steam turbine 1 is lowered, so that the effect of reducing the height of the entire building and reducing the construction cost can be obtained.

  By installing the pump 8 in the return circulation water pipe 5, the hot well level L6 of the condenser 2 can be raised as described in the above a).

  For this reason, the hydrostatic head difference with the cooling tower water spray pipe 7 installed in the upper part of the cooling tower 4 becomes small, and it is possible to make the head of the circulating water pump 6 small. Further, as described in i) above, since it is not necessary to increase the height L5 of the cooling tower 4, the installation level L9 of the cooling tower sprinkling pipe 7 does not increase accordingly, and the head of the circulating water pump 6 is reduced. Therefore, the construction cost can be reduced.

(Embodiment 2)
A condensing device for an axial exhaust steam turbine according to Embodiment 2 of the present invention and a geothermal power plant including the same will be described with reference to FIG. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The second embodiment is different from the first embodiment in that the return circulation water pipe 5 further includes a hydraulic or pneumatic shutoff valve 10 as well as the pump 8. In relation to the shutoff valve 10, a failure detection device 31 and a control device 32 are provided.

  The failure detection device 31 detects this failure when the circulating water pump 6 or the regulating valve 9 or the circulating water pump 6 and the regulating valve 9 fails. When the failure detection device 31 detects a failure, the control device 32 controls the shutoff valve 10 to be shut off.

  As a result, when the circulating water pump 6 fails or when the flow rate cannot be adjusted by the control valve 9, or when the circulating water pump 6 and the control valve 9 fail and the hot well level L6 rises, the return is returned. By closing the shutoff valve 10 installed in the circulating water pipe 5, the inflow of circulating water from the cooling tower 4 to the condenser 2 can be shut off immediately. Thereby, even if the difference between the hot well level L6 restricted by the amount of circulating water flowing into the condenser 2 and the installation level L8 of the steam turbine 1 is set to be small, it is possible to prevent the wake-up action. Thereby, as described in the first embodiment, the hot well level L6 can be raised to reduce the digging level L3 of the condenser 2, and the construction cost can be reduced.

(Embodiment 3)
A condensing device for an axial exhaust steam turbine according to Embodiment 3 of the present invention and a geothermal power plant including the same will be described with reference to FIG. The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  The third embodiment is different from the second embodiment in that the return circulating water pipe 5 has a regulating valve 11 instead of the shutoff valve 10. In association with the control valve 11, a failure detection device 31 and a control device 32 are provided.

  The failure detection device 31 detects this failure when the circulating water pump 6 or the regulating valve 9 or the circulating water pump 6 and the regulating valve 9 fails. When the failure detection device 31 detects a failure, the control device 32 controls the adjustment of the flow rate in the control valve 11.

  When the circulating water pump 6 fails or when the flow rate cannot be adjusted by the control valve 9 and the hot well level L6 becomes high, the flow rate of the control valve 11 installed in the return circulating water pipe 5 instead of the shut-off valve 10 is reduced. By controlling the adjustment, the amount of circulating water flowing into the condenser 2 can be limited. As a result, the difference between the hot well level L6 restricted by the amount of circulating water flowing into the condenser 2 and the installation level L8 of the steam turbine 1, that is, the height required for storing the cooling water is reduced, and the level L6 Even when the difference between L8 and L8 is set small, it is possible to prevent the warning action.

  Thereby, it is not necessary to lower the hot well level L6, and it is not necessary to lower the digging level L3 of the condenser 2, so that the construction cost is reduced.

  Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the technical scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the technical scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Steam turbine 2 Spray type direct contact type condenser 3 Spray nozzle 4 Cooling tower 5 Return circulating water pipe 6 Circulating water pump 7 Cooling tower water spray pipe 8 Pumps 9 and 11 Control valve 10 Shut-off valve 20 Turbine building 31 Fault detection device 32 Control apparatus

Claims (7)

A condenser that condenses the steam exhausted from the steam turbine by directly contacting cooling water from the spray nozzle;
A cooling tower that receives and accumulates water condensed by the condenser and generates the cooling water;
A circulating water pipe for supplying the water condensed by the condenser to the cooling tower;
A return circulation water pipe for supplying the cooling water generated by the cooling tower to the condenser;
With
A condensing device for an axial exhaust type steam turbine, wherein a pump is disposed in the return circulation water pipe.   The pump has a hydrostatic head difference obtained by subtracting the water surface level of the cooling tower from the maximum installation height of the spray nozzle of the condenser from the pressure difference obtained by subtracting the internal pressure of the condenser from the internal pressure of the cooling tower. The condensing device for an axial exhaust steam turbine according to claim 1, wherein the subtracted value satisfies a required pressure of the spray nozzle.   The condensing device for an axial exhaust steam turbine according to claim 1 or 2, further comprising a shut-off valve disposed in the return circulation water pipe.   3. The condensing device for an axial exhaust steam turbine according to claim 1, wherein a first control valve for adjusting a flow rate is further arranged in the return circulation water pipe. A circulating water pump provided in the circulating water pipe for supplying the water condensed by the condenser to the cooling tower, and a second regulating valve for adjusting a flow rate of the water condensed by the condenser; When,
A failure detection device for detecting a failure of each of the circulating water pump and the second control valve;
A control device that shuts off the shuttable valve when a failure of the circulating water pump or the second regulating valve, or the circulating water pump and the second regulating valve is detected by the failure detection device;
The condensing device for an axial exhaust steam turbine according to claim 3, further comprising: A circulating water pump provided in the circulating water pipe for supplying the water condensed by the condenser to the cooling tower, and a second regulating valve for adjusting a flow rate of the water condensed by the condenser; When,
A failure detection device for detecting a failure of each of the circulating water pump and the second control valve;
When the failure detector detects a failure of the circulating water pump or the second regulating valve, or the circulating water pump and the second regulating valve, the flow rate of the return circulating water pipe is adjusted to the first regulation A control device that regulates by a valve;
The condensing device for an axial exhaust steam turbine according to claim 4, further comprising: A condensing device for an axial exhaust steam turbine according to any one of claims 1 to 6,
The steam turbine that is provided with steam and exhausts the worked steam to the condenser;
A generator for generating electric power by being supplied with rotational energy by the steam turbine;
A geothermal power plant characterized by comprising:

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